1. Field of the Invention
This invention relates in general to spreading a bedding material within a ditch, and in particular to a method and apparatus for spreading sand in a ditch to provide a compliant bedding layer for laying a pipe upon.
2. Description of the Prior Art
A typical method for spreading bedding material within a ditch to provide a bedding layer for laying a pipe on is to, by means of an excavator such as a backhoe, dump the bedding material within the ditch. Then, shovels and the like are used by manual laborers to spread the bedding material by hand. This method is very labor intensive and may not efficiently achieve desired results for the bedding layer. For example, the bedding material may need to be screened and spread to a uniform consistency and height as is typically specified for bedding layers for laying pipe upon.
Spreading devices for spreading different materials upon a ground surface can be seen in several prior art patents. For example, U.S. Pat. No. 5,174,685, issued to Buchanan, on Dec. 29, 1992, discloses a flexible pipe laying and covering apparatus which has a vertically shiftable scraper for adjusting the height of fill material. Further, U.S. Pat. No. 4,714,381, issued on Dec. 22, 1987, and U.S. Pat. No. 4,741,646, issued on May 3, 1988, and both invented by Hatch, disclose a machine for laying conduit and methods for use thereof having an adjustable leveler gate which is formed by a vertical plate.
Often, pipe laying applications require that pipes are laid in a compliant bedding layer to prevent damage to the pipes which may occur from shifting soil and heavy loads applied to a ground surface beneath which the pipes are berried. In such cases, a compliant bedding layer is required, such as one that can be obtained utilizing sand rather than stones or rocks.
U.S. Pat. No. 4,464,715, issued to Ashbaugh, on Jul. 31, 1984, discloses a system for the one-step dewatering of a trench and the construction of a pipeline bed which includes horizontal plates for controlling the height of a bedding layer. However, the horizontal plates disclosed in Ashbaugh are not readily adjustable for selecting the vertical thickness of the bedding layer. Further, the bedding material disclosed in Ashbaugh is stone, and not sand.
U.S. Pat. No. 5,158,394, issued to Bresnahan, on Oct. 27, 1992, discloses a spreader device having an L-shaped bar which is adjustable to set a height of sod spread on an open field, such as a golf course. However, the spreader device in Bresnahan is for spreading particulate matter on an open field, and not intended for laying a bedding layer for a pipe in a ditch.
When a compliant bedding layer is required, such as one provided by depositing sand, often a maximum particle size is specified for the bedding material. Sand may often be presorted to remove large particles above a particular size, however, sand is often received at an excavation site which includes rather large particles which would interfere with providing a compliant bedding layer. Frequently, different particle sizes may be specified such that it is desirable to have a readily removable and readily interchangeable screening device.
U.S. Pat. No. 4,741,646, issued on May 3, 1988, and invented by Hatch, discloses a machine for laying conduit and methods for use thereof, which is briefly discussed above. Hatch discloses a screen for covering an upper opening for passing fill material therethrough. However, Hatch does not disclose a readily removable screen which may be interchanged for selectively preventing particulate matter above a certain size from entering a prior art bedding layer spreader.